1. Field of the Invention
This invention pertains to lifting and propulsion systems in vertical and short takeoff and landing type aircraft. More particularly, this invention pertains to such systems wherein the power source is a bypass turbofan engine and where remote lifting fans are powered by turbojet exhaust while bypass fan efflux is vectored to provide lift or thrust.
2. Description of the Prior Art
Gas turbine powered aircraft for making vertical or short takeoffs and landings have used a variety of configurations. Some of such aircraft use one or more turbojet engines and vector the engine exhaust downward to create lift. Once airborne, these craft gradually vector the thrust aft until forward airspeed is sufficient to support the aircraft, at which point conventional aerodynamics take over. Other configurations have used remotely located lifting fans powered by compressor stage bleed air from the turbojet engines, or have ducted a mixture of compressor bleed air and turbojet exhaust gas to remotely located nozzles which discharge downward, thereby creating reaction lifting forces which lift and control the aircraft.
The critical period in the flight of a vertical and short takeoff and landing aircraft is at the transition between hover and forward flight. While forward airspeed is yet insufficient to support the aircraft, engine power used to lift the aircraft must be diverted to drive the aircraft forward, leaving less power available for sustaining altitude while forward airspeed increases. The present invention provides a means for gradually deflecting bypass fan efflux aft while maintaining altitude with a plurality of turbojet exhaust gas powered lifting fans, thereby enabling a smooth and controlled transition.